THE GREAT YEAR
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Confusion of precession and Platonic year
The Great Year, based on the cycle of precession, is often called Platonic year based on a confusion with a concept defined by the philosopher Plato, who in his Timaeus defined the "perfect year" as the return of the celestial bodies (planets) and the fixed stars (circle of the Same) to their original positions:
“ And so people are all but ignorant of the fact that time really is the wanderings of these bodies, bewilderingly numerous as they are and astonishingly variegated. It is none the less possible, however, to discern that the perfect number of time brings to completion the perfect year at that moment when the relative speeds of all eight periods have been completed together and, measured by the circle of the Same that moves uniformly, have achieved their consummation." ”
The Platonic year, based on the revolution of the planets and estimated by Macrobius as lasting 15,000 solar years, has no connection to the "precessional period of 36,000 years", caused by the slow gyration of the Earth's axis and discovered by the Greek astronomor Hipparchus:
“ Some time around the middle of the second century BC, the astronomer Hipparchus discovered that the fixed stars as a whole gradually shifted their position in relation to the annually determined locations of the Sun at the equinoxes and solstices... Otto Neugebauer argued that Hipparchus in fact believed that this [36,000 years] was the maximum figure and that he also computed the true rate of one complete precession cycle at just under 26,000 years... ”
The confusion originates with the astronomer Ptolemy, who "adopted the larger, erroneous, figure, with the result that henceforth the two versions of the Great Year - the Platonic Great Year, defined by the planets, and the precessional, defined by the stars - were to be increasingly confused."
"Some people called it the Yuga cycle, others called it the Grand cycle and others the Perfect Year...But the most common name found in use from ancient Europe to ancient China, was simply the Great Year".
Astronomical value of the precession cycle
The empirical data for the precession of the equinox do not warrant the extrapolation to a full cycle and from the antiquity to Modern times many scholars doubted its existeance. Astronomical phenomena often exhibit a movement within a limited range and it was surmised the the displacement of the vernal point is of this type. Known as the theory of trepidation the idea is traced back to Theon of Alexandria (4th.c) who credits it to older astrologers. In the middle ages it was favored by Arabian astronomers and Copernic also endorsed it. As the name 'trepidation' suggests it was not considered to be a 'year' which is most commonly thought as circular. The duration of the precession cycle, the time it takes for the equinox to precess 360 degrees relative to the fixed stars, is often given as 25,920 or 26,000 years. In reality the exact duration cannot be given, as the rate of precession is changing over time. This speed is currently 243.8 microradians (50.3 arcseconds) per year which would give 25,765 years for one cycle to complete. The precessional speed is slightly increasing each year, and therefore the cycle period is decreasing. Numerical simulations of the solar system over a period of millions of years give a period of 257 centuries. but no one is certain of the exact precession rate over long periods of time.
Near the turn of the 20th century astronomer Simon Newcomb invented a "constant" to account for the increasing annual precession rate. Over the last 100 years this constant has been found to have underestimated the actual acceleration in the rate.
Early cultures and mythology
The Greeks broke the Great Year into four ages known as the Golden, Silver, Bronze, and Iron Ages,which add to one half of a precessional cycle[Or about one Platonic Great Year]. The Indian Great Year cycle Yugas is also broken into four periods; the Satya, Treta, Dvapara, and Kali yugas, and also add to one half a precessional cycle, as calculated by the Indian sage Sri Yukteswar Giri. In his book, The Holy Science, first published in 1894 as Kaivalya Darsanam, Yukteswar describes the Great Year as a period of time wherein the earth goes through a "complete change, both externally in the material world, and internally in the intellectual or electric world" with four rising ages and four descending ages, equal in length to one complete precession of the equinox. Other Indian scholars put the length at millions of years, a period of time unrelated to the precession cycle.
According to Giorgio de Santillana, the late Professor of the History and Philosophy of Science at M.I.T and Hertha von Dechend, in their book Hamlet's Mill, published in 1969 by Gambit, there are over 200 myths or folk stories from over thirty ancient cultures that refer to a Great Year tied to the movement of the equinox or the motion of the heavens.
Significance in astrology
Most astrologers use a precession rate rounded to 50 arc seconds per year to derive a Great Year period of 25,920 years, the period required for the equinox to move through all twelve of the classic zodiacal signs. Some, such as Boris Cristoff prefer to round the age of one sign of the zodiac to 2100 years, which equates to a Great Year duration of 25,200 years.
1.^ ."The difficulty with the term "great year" lies in its ambiguity. Almost any period can be found sometime or somewhere honored with this name." - noted an eminent specialist: Neugebauer O., (1975)A History of Ancient mathematical astronomy, Birkhäuser, p.618
2.^ Plato, Timaeus 39d, in John M. Cooper (ed.), "Plato: Complete Works" (Hackett Publishing Company, 1997), p. 1243
3.^ William Harris Stahl, "Macrobius: Commentary on the Dream of Scipio" (Columbia University Press, 1952), p. 21
4.^ a b Nicholas Campion, "The Great Year: Astrology, Millenarianism and History in the Western Tradition" (Arkana/Penguin Books, 1994), p. 246–247.
5.^ Walter Cruttenden, "Lost Star of Myth and Time" (St. Lynn's Press, 2006), p.xix–xx. 6.^ A.L. Berger; Obliquity & precession for the last 5 million years; Astronomy & astrophysics 51 (1976), 127
Astrological age, Axial precession (astronomy), Precession, Precession: Astronomy, Yuga
The Platonic version of the Great Year is taken to be identical to the conception of Aristotle, who stated that the wnter of the Great Year was a Cataclysmos or Flood and that the summer of the Great Year was an Ekpyrosis or world-destroyed-in-Flames: naturally these two events were supposed to have taken some thousands of years in between, in fact one-half of the Great Year. Macrobius stated the Platonic period to have been 15000 years and half of that would be 7,500 years: we can surmise by the repeated statements of a period of 8000 years in the Atlantis dialogues that he rounded that one-half cycle up and he considered the cycle to have been 16000 years in all. I do not believe Aristotle gave an estimation for the Great Year which survives. However the date is quite readily supported by both Greek and Indian estimates for the time since the Golden Age, which was estimated to have begun about 12000 BC and ended by "9000 years ago" in the Platonic reckoning.[8000+1000 years roughly before Plato for Phaethon]
Plato is definitely saying that the Greatest Deluge of All was the Cataclysmos of the last Great Year and the Phaethon Event is the Ekpyrosis following it at about 8000 years later: it is also implicit that Plato considered the Flood of Deucalion to have occured after the Phaethon event and probably immediately following it, as it is given in some versions of the Myth.